CALIFORNIA, U.S. - Amid a dramatic price surge, Bitcoin worth $70 million was stolen by hackers.

Bitcoin, which has gained more than $5,000 in just the past two days, surged past $17,000 on Thursday, as frenzy surrounding the virtual currency escalated.

Fresh concerns were raised about the security of bitcoin and other virtual currencies after NiceHash, a company that mines bitcoins on behalf of customers, said it is investigating a breach.

The breach has reportedly resulted in the theft of about $70 million worth of bitcoin.

According to research company Coindesk, a wallet address referred to by NiceHash users indicates that about 4,700 bitcoins had been stolen.

In a statement, NiceHash said it will stop operating for 24 hours while it verifies how many bitcoins were taken.

According to Coinbase, which is the largest bitcoin exchange, as of 11:15 a.m. EST, bitcoin was valued at $17,482.

In comparison, at the start of the year, one bitcoin was worth less than $1,000.

The price surge and the NiceHash hack occurred just as the trading community prepares for bitcoin to start trading on two established U.S. exchanges.

On Sunday evening, futures for bitcoin will start trading on the Chicago Board Options Exchange and on crosstown rival CME Group's platforms later in the month.

Some investors believe that bitcoin, the world's most popular virtual currency, is gaining in mainstream legitimacy after several countries, including China, tried to stifle the virtual currency.

NiceHash has said in a statement, “The incident has been reported to the relevant authorities and law enforcement and we are cooperating with them as a matter of urgency,” where it also urged users to change their online passwords.

The case is being investigated by the Slovenian police together with authorities in other states.